Compositions and process for recovering subterranean oil using green non-toxic biodegradable strong alkali metal salts of polymerized weak acids

Abstract

Compositions and process for recovering of oil from subterranean oil-bearing reservoirs consisting of green non-toxic biodegradable strong alkali metal salt of polymerized weak acids, one or more surfactants, an aqueous fluid, a optionally one or more mobility control agents and optionally one or more co-solvents are disclosed. Such compositions are injected into the reservoir through one or more injection wells and assist in recovering trapped oil through one or more producing wells. A preferred green non-toxic biodegradable strong alkali metal salt of polymerized weak acids is the sodium salt of polyaspartic acid shown below where n is 10 to 50. The compositions and the process of the present invention offer the advantage of improved compatibility with unsoftened waters, surfactants, and various mobility control agents. The green non-toxic, biodegradable properties of the alkali makes it particularly suitable for environmentally sensitive applications such as offshore and inland lakes.

1 . A composition for recovering oil from subterranean oil-bearing formations comprising:
 a) green non-toxic biodegradable strong alkali metal salt of polymerized weak acids,   b) one or more surfactants,   c) an aqueous solvent,   f) optionally one or more mobility control agents, and;   g) optionally one or more co-solvents.   
   
   
       2 . The composition of  claim 1  where the green non-toxic biodegradable strong alkali metal salt of polymerized weak acids is the sodium or potassium alkali metal salt of a polymerized weak acid. 
   
   
       3 . The composition of  claim 1  where the preferred green non-toxic strong alkali metal salt of a polymerized weak acid has the following structure where n is 10 to 50. 
     
       
         
         
             
             
         
       
     
   
   
       4 . The composition of  claim 1  where the green non-toxic biodegradable strong alkali metal salt of polymerized weak acids is used from about 0.01% to about 5.0% by weight of the total composition. 
   
   
       5 . The composition of  claim 1  where the surfactant is one or more from the group anionic, cationic, amphoteric surfactant. 
   
   
       6 . The composition of  claim 1  where the surfactant is used from about 0.025% to about 5.0% by weight of the total composition. 
   
   
       7 . The composition of  claim 1  where the aqueous solvent is water, water-alcohol solutions, solutions of various salts in water such as oilfield injection brines and produced brines as well as synthetic brines. 
   
   
       8 . The composition of  claim 1  where the mobility control agent is one or more synthetic or natural polymers such as polyacrylamide, partially hydrolyzed polyacrylamide, xanthan gum, hydroxymethyl cellulose and guar gum. 
   
   
       9 . The composition of  claim 1  where the mobility control agent is used from about 0% to about 1% by weight of the total composition. 
   
   
       10 . The composition of  claim 1  where the co-solvent is a low molecular weight alcohol, glycol or ether. 
   
   
       11 . The composition of  claim 1  where the co-solvent is used from about 0% to about 20% by weight of the total composition. 
   
   
       12 . A process for recovering oil from subterranean oil-bearing reservoirs by injecting a composition containing green non-toxic biodegradable strong alkali metal salt of polymerized weak acids, one or more surfactants, an aqueous solvent, optionally one or more mobility control agent, and optionally one or more co-solvents into one or more injection wells and recovering the oil from one or more producing wells. 
   
   
       13 . The process for recovering oil from subterranean reservoirs of  claim 12  where the green non-toxic biodegradable strong alkali metal salt of polymerized weak acids is the sodium or potassium alkali metal salt of a polymerized weak acid. 
   
   
       13 . The process for recovering oil from subterranean reservoirs of  claim 12  where the green non-toxic biodegradable strong alkali metal salt of polymerized weak acids has the following structure where n is 10 to 50: 
     
       
         
         
             
             
         
       
     
   
   
       14 . The process for recovering oil from subterranean reservoirs of  claim 12  where the green non-toxic biodegradable strong alkali metal salt of polymerized weak acids is used from about 0.01% to about 5.0% by weight of the total composition. 
   
   
       15 . The process for recovering oil from subterranean reservoirs of  claim 12  where the surfactant is one or more from the group anionic, cationic, amphoteric surfactant. 
   
   
       16 . The process for recovering oil from subterranean reservoirs of  claim 12  where the surfactant is used from about 0.025% to about 5.0% by weight of the total composition. 
   
   
       17 . The process for recovering of oil from subterranean reservoirs of  claim 12  where the aqueous solvent is water, water-alcohol solutions, solutions of various salts in water such as oilfield injection brines and produced brines as well as synthetic brines. 
   
   
       18 . The process for recovering oil from subterranean reservoirs of  claim 12  where the mobility control agent is one or more synthetic or natural polymers such as polyacrylamide, partially hydrolyzed polyacrylamide, xanthan gum, hydroxymethyl cellulose and guar gum. 
   
   
       19 . The process for recovering oil from subterranean reservoirs of  claim 12  where the mobility control agent is used from about 0% to about 1% by weight of the total composition. 
   
   
       20 . The process for recovering oil from subterranean reservoirs of  claim 12  where the co-solvent is a low molecular weight alcohol, glycol or ether. 
   
   
       21 . The process for recovering oil from subterranean reservoirs of  claim 12  where the co-solvent is used from about 0% to about 20% by weight of the total composition. 
   
   
       22 . The process for recovering oil from subterranean reservoirs of  claim 12  where the surfactant is capable of lowering the interfacial tension between the composition and oil to values below 10 −1  mN/m in the presence of the green non-toxic biodegradable strong alkali metal salts of polymerized weak acids.